The objective of this study is to characterize the periodontal status in an adult population, as part of the assessment of environmental, microbiological and host response risk factors. We propose that periodontal disease develops secondary to subgingival infection by specific periodontal pathogens transmitted from an exogenous source. However, the importance of environmental factors, facilitating the colonization of the specific microorganisms involved, will be further addressed. The environmental factors to be assessed include demographics, socioeconomic status, oral hygiene, local irritant levels, oral disease, utilization of professional services, habits, medication, and diseases such as diabetes. In addition, life events, daily stress and distress will be assessed to determine their importance as risk factors for development of periodontal disease. We propose to utilize a large group of subjects (approximately 2,500) selected by a random process from an urban/suburban population. The group will be thoroughly examined on a triennial basis to provide information for analyses of, 1) cross-sectional and 2) longitudinal data regarding pertinent clinical, microbiology and host response factors. Data will be analyzed to assess the relative importance of these factors in identifying a risk profile for periodontal disease. A subgroup exhibiting severe periodontal disease culled from the sample at the initial examination, will be monitored every six months by the use of a constant force electronic probe for changes in attachment level. Also, serial standardized periapical radiographs will be taken for radiographic bone mass/density assessments by digitized computer subtraction techniques. These new methodologies will make it possible to assess the progression of periodontal disease and to identify cycles of active and inactive tissue destruction, and to relate environmental, microbiological and host response factors to disease activity. In addition, families of probands with severe periodontal disease will be examined in preparation for detailed studies of the transmission of putative periodontal pathogens. These studies will provide significant new information which will be used to determine a high risk profile for periodontal disease, so that subjects exhibiting this profile can be targeted for interceptive therapies preventing the development of periodontal disease.